Rapid and Sensitive Spectrophotometry. II. A Stopped-Flow Attachment for a Stabilized Quartz Spectrophotometer

The stabilization of the light sources and the photocell circuits of a quartz spectrophotometer and the design of suitable stopped flow apparatuses are described. The latter have been designed for 1.6- and 10-mm optical paths and have been shown to give rapid mixing (<0.1 sec). Errors of optical density measurement are diminished by rectangular observation tubes, and errors of extinction coefficients are minimized by a narrow spectral interval (less than 2 mμ from 230–600 mμ). The error of optical density caused by the photoelectric circuits is about 1×10−4 for a response time (10–90 percent) of 1 sec. The application of this apparatus to the measurement of rapid chemical reactions in the visible and ultraviolet regions is described.